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+ name the different type of scrapers, * state the features of each type of scrapper, , , , + state the precaution to be observed while uses scrapper., , , , Scraper is a hand tool which is used to scrap the workpiece, surface by removing the smallest metal particles., Application, , It is used to obtain a smooth non scored and uniformly, bearing surface which is required for sealing, sliding and, guiding surface., , In automobiles it is used to remove carbon particles from, cylinder head, piston head and manifold pipes, , Itis also used to scrap the bearings of cranks halt and, sometimes the cylinder liner., , Type of scrapers, , 1. Flat scraper, , 2. Special scraper, , Flat scraper, , The cross section of this scraper is Flat. The cutting edge, has Flat surface., , Use, , Itis used to scrap the high spots of a flat Surface, , Special Scrapper, , Special scrapers available for scraping and finishing curved, surfaces., , They are :, , ~ half round scraper, - three-square scraper, - bull nose scraper, , Half round scraper, , The cross- section of this scraper is a segment and it, tapers to a rounded point (Fig 1), , , , Fig 1, , Sal., , The round bottom face is curved and is hollow in the middle., , The bottom facet and the flat surfaces are ground along, the edge to form the cutting edge. (Fig 2), , The cutting angle is between 45° and 65°., , , , , , , , , , , , Fig2, FLAT GROUND, (ON ROUNDED Back, , , , , curmne, EDGE, , The curvature at the cutting edge helps to make point, contact while scraping, and also helps to remove small, spots. (Fig 3), , , , , , Fig 3, , Ui,, , Three- square scraper (Fig 4), , , , , , , , This scraper is used for scraping small diameter holes, and deburring the edges of holes., , The cross-section of this is triangular. This has more, number of cutting edges and the hollow portion between, the cutting edges helps in re-sharpening easily., , , , Fig 4, , SSS, , (CROSS SECTION, , , , Bull nose scraper (Fig 5), , This scraper has the cutting edge shaped into a flat circular, disc. The cutting edge forms about two thirds of the circle., , , , , , Fig 5, , , , , , , , , , 24 Automobile : Mechanic Diesel (NSQF LEVEL - 4) Related Theory for Exercise 1.2.09, , , , Itis useful for scraping large bearings. (Fig 6) This scraper, can be used in a longitudinal direction lika a flat scraper, or with a circumferential movement like a half round, scraper. This dual action helps to prevent ridges on the, scraped surfaces., , , , Always use scrapers with firmly fitted handles., , Protect the cutting edges with a rubber cover, when not in use., , Apply oil or grease on the cutting edges when, notis use., , , , , , , , , , Fig 6